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Interstitial fauna of the
Galapagos: Porrocystidinae
(Platyhelminthes
Polycystididae)
a
T. J. Artois & E. R. Schockaert
a
a
Research Group Zoology, Department of Chemistry,
Biology and Geology, Limburgs Universitair Centrum,
B-3590, Diepenbeek, Belgium E-mail:
Version of record first published: 01 Aug 2012.
To cite this article: T. J. Artois & E. R. Schockaert (1999): Interstitial fauna of the
Galapagos: Porrocystidinae (Platyhelminthes Polycystididae), Tropical Zoology, 12:2,
309-324
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Tropical Zoology 12: 309-324, 1999
Interstitial fauna of the Galapagos:
Porrocystidinae (Platyhelminthes Polycystididae)
T.J.
ARTOIS
and E.R.
SCHOCKAERT
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Research Group Zoology, Department of Chemistry, Biology and Geology, Limburgs
Universitair Centrum, B-3590 Diepenbeek, Belgium (E-mail: tom.artois@luc.ac.be)
Received 9 February 1999, accepted 14 June 1999
Three new species, from the Galapagos Isles, of the ill-defined taxon Porrocystidinae Evdonin 1977 are described. Austrorhynchus galapagoensis n. sp. is
mainly characterized by the shape of the male accessory organ. The other two
species represent new genera: Galapagorhynchus hoxholdi n. gen. n. sp. and Pygmorhynchus pygmaeus n. gen. n. sp. The main characteristics of Galapagorhynchus n. gen. are the presence of hard teeth in the male atrium, the lack of an
accessory stylet, the long spermatic ducts and the very elongated common genital atrium. Pygmorhvnchus n. gen. lacks an accessory stylet, has short but
strongly muscular spermatic ducts and has nuclei near the junction of the epithelia of the proboscis sheath and cone. The systematic positions of the three
new taxa are discussed, and a brief phylogenetic analysis of the Porrocystidinae
is given. Diagnoses of the new taxa are given, and the diagnosis of the subfamily
Porrocystidinae is emended.
KEY WORDS:
Porrocystidinae, Polycystididae, Galapagos, new taxa, phylogeny.
Introduction
Material and methods
Abbreviations
Results
Austrorhynchus galapagoensis n. sp.
Galapagorhynchus hoxholdi n. gen. n. sp.
Pygmorhynchus pygmaeus n. gen. n. sp.
General discussion
Diagnoses
Acknowledgements
References
309
310
310
310
310
313
317
321
323
324
324
INTRODUCTION
Thirty-three species of Kalyptorhynchia were present in the material collected
by S. Hoxhold and P. Schmidt during the Galapagos Project of the Zoological Institute II of the University of Gottingen (see Ax & ScHMIDT 1973). The species of
T.J. Artois and E.R. Schockaert
310
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Schizorhynchia were studied by NOLDT & HoXHOLD (1984). Of the Eukalyptorhynchia, only one species has been discussed in the literature: Polycystis ali f. 'Galapagos' Schockaert 1982 (KARLING 1986). The other Polycystididae and two Koinocystididae were the subject of an unpublished work by I. Henze (Diplomarbeit, University of Gottingen, 1987). Some of the new taxon names proposed here are in fact
names from that work.
In this first contribution on the Eukalyptorhynchia of the Galapagos, we
describe three new species of Polycystididae, one belonging to the genus Austrorhynchus Karling 1952. To classify the other two, we erect new genera, Galapagorhynchus n. gen. and Pygmorhynchus n. gen. All three genera belong to the Porrocystidinae Evdonin 1977.
This contribution is part of a series of papers describing the meiofauna of the
Galapagos Isles. A survey of these papers can be found in MIELKE (1997).
MATERIAL AND METHODS
Details of sampling procedures and localities are provided by Ax & ScHMIDT (1973). The
Eukalyptorhynchia were collected by S. Hoxhold and P. Schmidt, who also studied the living
animals. The measurements of body length are those made by S. Hoxhold on live material.
Measurements of hard parts given herein are always taken axially using S. Hoxhold's measurements on live material as a scale. Paraffin sections (4 Jlm) were stained with Heidenhain's
iron hematoxylin with eosin as counterstain.
Figures without a scale are freehand.
Brief locality data are followed by a number that refers to the detailed descriptions of
these localities in Ax & ScHMIDT (1973: 21-26).
Type material will be deposited in the Zoological Museum of the University of Gottingen.
ABBREVIATIONS
acg: accessory glandular organ; b: female bursa; br: brain; ca: common atrium; de: ejaculatory duct; ds: spermatic duct; e: eye; g: glands; gp: gonopore; m: muscle; rna: male atrium;
mb: male bursa; od: oviduct; ov: ovarium; p: proboscis; ph: pharynx; s: stylet; sph: sphincter;
ss: accessory stylet; t: testis; ut: uterus; vg: prostate vesicle; vi: vitellarium; vid: vitelloduct; vs:
vesicula seminalis.
RESULTS
Austrorhynchus galapagoensis n. sp. (Figs 1-2)
Locality. Santa Cruz: Bahia Academy: northern side (IX. Sb) (type locality).
Material. Drawings and photographs of live material by Dr Siegmar Hoxhold. Nine serially sectioned animals, a frontally sectioned animal designated as holotype.
Derivation of species name. Named after the Galapagos Isles.
Porrocystidinae of the Galapagos
311
Description. Animals about 0.5-0.6 mm long, with two eyes. The proboscis is
about 20% of the body length (measured about 120 Jlm in one live animal).
The internal organization corresponds with that of the other Austrorhynchus
species. The main differences are in the shape and dimensions of the hard structures. The double-walled prostate stylet is very short, about 21 Jlm long. It bears no
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B
ph
B-C
20J,lm
vs
vg
s
ss
ut
gp
mb
vi
sph
c
ov
b
D
Fig. 1. -- Austrorhynchus galapagoensis n. sp. A, general structure; B, accessory stylet; C, stylet; D,
organisation of the atrial organs; (all from live animals).
312
T.J. Artois and E.R. Schockaert
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hook, and the tube is half as long as the funnel. As in all Austrorhynchus species,
the inner stylet is about half as long as the outer stylet, and is found in the distal
half of the latter. The accessory stylet (A-organ) is relatively simple, consisting of a
Fig. 2. - Austrorhynchus galapagoensis n. sp. A, caudal body end showing the atrial organs and the
pharynx; B, female organs and male bursa; C, stylet and accessory stylet; (all from live animals).
Porrocystidinae of the Galapagos
313
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ring and a flagellum (terminology of KARLING 1977). The ring is 36 ).liD long and,
distally, 31 ).liD wide; the flagellum is 41 ).liD long. Distally, the ring bears a comb,
while no comb is found on the flagellum.
A widening of the male atrium, filled with sperm in all the specimens examined, can be regarded as a male bursa. Diffuse accessory glands enter the male atrium near the seminal duct.
The organization of the female system is identical to that of Austrorhynchus
scoparius Brunet 1965. A large bundle of eosinophilic glands enters the bursal
stalk. In orie specimen the uterus contains an egg.
Discussion. Two other Austrorhynchus species have a more or less ring-shaped
A-organ: A. calcareus Kading 1977 and A. magnificus Kading 1952. Their A-organs
have only a small "window" (KARLING 1977), and do not show a true annular structure as does the A-organ of the new species. Furthermore, the stylet of these two
species bears a short hook. They have only been found in the South Atlantic.
Among the Austrorhynchus species that occur in the Pacific or the Indian
Ocean, only A. pacificus Kading 1977 and A. californicus Kading 1977 have Aorgans resembling that of A. galapagoensis in many respects. The A-organs of Karling's species, however, are very thin plates and not rings. Bearing this in mind, the
A-organ of A. galapagoensis should be re-examined carefully on whole mounts. If
the A-organ is in fact a plate instead of a ring, A. pacificus is likely to be the sister
species, because the stylet has no hook. The stylet of A. californicus has a hook, as
in most Austrorhynchus species. If it is really an open ring, then A. galapagoensis is
unique in the Pacific. Such a ring can result from fusion of the style and the foot
(terminology of KARLING 1977) as in the A-organs of A. hawaiiensis Kading 1977
and A. maldivarum Kading 1977, and one of those species might be the sister species. For details of the possible evolution of the A-organ: see KARLING 1977.
Galapagorhynchus hoxholdi n. gen. n. sp. (Figs 3-5)
Localities. Santa Cruz: Bahia Academy: north side (IX. 5b) (type locality).
Santa Cruz: Bahia Academy: southern beach (IX. 6b).
Material. Drawings and photographs of live animals by Dr Siegmar Hoxhold. A total of
30 animals serially sectioned, a frontally sectioned animal designated as holotype.
Derivation of name. Genus name refers to the Galapagos Isles. Species name
in honour of Dr S. Hoxhold.
Description. Animals 1.4-1.9 mm long, opaque orange to red, without eyes.
The epidermis is syncytial containing numerous empty vacuoles and numerous
rhabdites that are 1/3 of the epithelium height. Rhabdites are absent around the
proboscis pore.
The proboscis is of the normal polycystidid type, with six fixators. It is 1520% of the body length. The proboscis sheath is lined with a low, nucleated epithelium and is surrounded by an inner circular and an outer longitudinal muscle coat.
Proximally, the circular muscles are relatively thick. There are no nuclei at the
junction of the sheath and cone epithelia. There are four pairs of proboscis retractors and one weakly developed pair of ventral integument retractors.
314
T.J. Artois and E.R. Schockaert
The pharynx is of the normal polycystidid type, situated in the first body half
and inclined forwards. There are two kinds of pharyngeal glands: eosinophilic and
basophilic ones. There are 24 internal pharyngeal longitudinal muscles. Around the
proximal third of the prepharyngeal cavity the longitudinal muscles are arranged iil
12 groups of ca 10 fibers each. The epithelium of the pharyngeal lumen is relatively
high, but lacks intraepithelial nuclei.
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A
B
c
Fig. 3. - Galapagorhynchus hoxholdi n. gen. n. sp. A, general structure; B, stylet; C, male atrial
organs; (all from live animals).
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Porrocystidinae of the Galapagos
315
Male and female gonads are paired. The testes lie dorsolaterally behind the
pharynx, extending from the caudal end of the pharynx to the proximal part of the
male atrium. The ovaries lie dorsolateral to the common gonopore, which is ventral
at ± 75%. The oocytes are arranged in rows. The vitellaria are dorsal to all other
reproductive organs and extend from behind the eyes to the caudal end of the body.
The common genital atrium is very long and tubiform, lined with a pseudociliation
(ruffled, degenerating epithelium), except in the most distal part, which can have a
nucleated epithelium. Inner circular and outer longitudinal muscle sheaths surround the atrium throughout its length.
The male atrium enters the common atrium laterally. It is rather long and
narrow. Its epithelium is degenerated to a pseudocuticula (leaving only the basement membrane)· and the musculature is the same as noted for the common atrium, at least for most of its length. The longitudinal muscles taper proximally,
where the circular muscles become thicker and multi-layered. The male atrium is
much broader here and is divided into two compartments. The most ventral one
receives the accessory glands and the ejaculatory duct, while the dorsal one contains the prostate stylet. The accessory organ consists of a large mass of coarsegrained basophilic glands and is surrounded by a thin, spirally running muscle
sheath. The seminal vesicles are paired, lined with a flat epithelium with flattened
nuclei and a more or less longitudinal muscle sheath. The ejaculatory duct is rather
broad at its proximal end, where it is lined with a high, nucleated epithelium. For
the rest of its length it has a very low epithelium. The ejaculatory duct runs very
near to, and dorsolateral from, the accessory glandular organ, entering the male
atrium just above the latter. It is surrounded by a circular muscle coat throughout
its length. An inner, more or less longitudinal muscle layer and an outer, thicker,
spiral, almost circular muscle sheath surround the prostate vesicle. The former
attaches to the inner side of the proximal end of the stylet, while the latter contin-
gp
Fig. 4. - Galapagorhynchus hoxholdi n. gen. n. sp. Reconstruction of the atrial system from the left
side.
T.J. Artois and E.R. Schockaert
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316
Fig. 5. - Galapagorhynchus hoxholdi n. gen. n. sp. A, habitus; B, male atrial organs; C, prostate vesicle and stylet; D, stylet; (all from live animals).
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Porrocystidinae of the Galapagos
317
ues in the muscle sheath of the male atrium. Ventrally, the outer muscles are continuous with a very thick muscle bundle that connects the prostate vesicle with the
accessory glandular organ and surrounds the distal part of the accessory organ.
There are two kinds of prostate glands: one producing an eosinophilic secretion,
the other a basophilic secretion. The nucleated parts of the prostate glands are
entirely extracapsular. The prostate secretions are discharged into the doublewalled stylet that is 94-108 J.Im long (m = 101, n = 2). The stylet is hook-shaped
with a complicated distal end with a pointed, upward-folded tip. The basal membrane of the proximal part of the male atrium forms numerous triangular teeth,
each about 3-4.5 J.Im long, with distally pointing tips. The distal part of the male
atrium is provided with diffuse, coarse-grained basophilic glands, and in some
specimens is swollen with sperm, thus functioning as a male bursa.
The female duct is short, entering the genital atrium caudally. Its distal part is
surrounded by a very thick sphincter. It ends caudally in the female bursa. Distal to
the sphincter the epithelium lining the female duct is pseudociliated, while proximal to the sphincter it is degenerated to a pseudocuticula. Proximal to the sphincter the female duct is surrounded by a thick circular muscle sheath. The bursa is
not well defined. It contains vacuoles filled with sperm and/or an eosinophilic
secretion. A short, common oviduct enters the female duct dorsally just behind the
sphincter. It is surrounded by a sphincter consisting of two fibers, and it almost
immediately splits into the two long oviducts. These are lined with a high, nucleated epithelium and with longitudinal muscles. Just before they reach the ovaries
they broaden and the vitelloducts enter the oviducts here. The spermatic (or insemination) ducts leave the female duct laterally. Distally these ducts are very narrow.
Here they are lined with a membranous epithelium and surrounded by a spirallyrunning, almost circular muscle coat. Proximally they broaden into seminal receptacles that are surrounded by a higher, irregular epithelium and a circular muscle
sheath. The spermatic ducts continue towards the ovaries as broad, muscular
ducts. The uterus of the normal polycystidid construction opens in the genital atrium close to the genital pore.
Discussion. See the general discussion.
Pygmorhynchus pygmaeus n. gen. n. sp. (Figs 6-7)
Localities. James: Bahia James: rockpools (VI. 1b) (type locality). Santa Cruz:
Bahia Academy: northern side (IX. 5d).
Material. Drawings and photographs of live animals by Dr Siegmar Hoxhold. A total of
8 serially sectioned specimens, a sagitally sectioned specimen designated as holotype.
Derivation of name. Both generic and species names refer to the very small
size. Pygmaios (Gr.): dwarf.
Description. The animals are very small, of maximum length 0.5 mm, and
with two eyes. The epidermis is syncytial with numerous vacuoles, some filled with
a light eosinophilic secretion. Rhabdites are lacking in most specimens, though in
some they were found in the ventral body wall of the anterior body half. Coarsegrained basophilic caudal glands are present.
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318
T.J. Artois and E.R. Schockaert
The proboscis is 116 to 115 of the body length, with a distinct apex. The
sheath epithelium is anucleated, with some delicate dilators. At the junction
between sheath epithelium and cone epithelium, some nuclei were observed. As in
all Polycystididae, there are six fixators. There is one well-developed pair of ventral
integument retractors, and four pairs of retractors: a dorsal, a dorsolateral, a lateral and a ventral pair, all weakly developed. Close to the proboscis, the dorsal retractors consist of about three fibers. More caudally, only one thicker fiber remains,
attached to the dorsal body wall. The lateral retractors also attach to the dorsal
body wall, while the dorsolateral and ventral ones attach to the ventral wall. Eosinophilic glands are present at both sides of the brain. Their necks extend towards
the proboscis pore.
The pharynx is situated in the first body half, has a short prepharyngeal cavity and is inclined forwards. As in some other polycystidids there is a ring of ruffled epithelium in the middle of the cavity. There are three kinds of pharyngeal
glands: two eosinophilic ones and a basophilic one. The basophilic glands open
into the pharyngeal lumen between the two eosinophilic glands. The epithelium of
the pharyngeal lumen lacks nuclei.
The gonads are paired. The testes are situated dorsolaterally and extend from
the pharynx to the level of the prostate vesicle. The ovaries are caudal, at both
sides of the body, rather small and globular, and contain only a few oocytes. The
vitellaria lie dorsal to all other reproductive organs, extending from the level of the
brain to the caudal end of the body, where they are joined. The gonopore is ventral
at ± 80%. The common genital atrium is lined with a low anucleated epithelium
and is surrounded by an inner circular and an outer longitudinal muscle layer.
The male atrium enters the common atrium dorsally. It is lined with a low
epithelium, and surrounded by an inner circular and thinner outer longitudinal
muscle sheath. Two relatively well separated compartments can be recognized in
the proximal part of the male atrium: the most ventral contains the prostate stylet,
the other receives the ejaculatory duct and. the accessory glands. The epithelium of
the anterior wall of the dorsal compartment is glandular and produces an eosinophilic secretion. The seminal vesicles are paired and lined with a very low epithelium showing some flattened nuclei. The ejaculatory duct is lined with the same epithelium. Both ejaculatory duct and seminal vesicles are surrounded by almost longitudinal muscles. The ejaculatory duct opens in the male atrium just beside the
accessory organ, whic}:l is surrounded by a circular muscle layer. It contains eosinophilic and basophilic glands, their nuclei being extracapsular. The eosinophilic
secretion has a smooth appearance in some specimens, in others it is clearly granular. At the distal end of the accessory organ four degenerated nuclei can be seen in
some specimens. The prostate vesicle is spindle-shaped, surrounded by a spiral
muscle coat that partly attaches to the inner side of the proximal end of the stylet.
The outer part of the muscle coat is continuous with the muscle coat of the male
atrium. The prostate glands (with extracapsular nucleated parts) produce a coarse
basophilic granular secretion. The prostate stylet is only 13.5 )liD long, tubiform
and slightly curved in its distal end. Without whole mounts, we were unable to
determine if it is double-walled, but it most probably is (as in a congeneric species
from Australia, presently being described by the authors).
The female duct enters the atrium at the caudal side, ending in the bursa,
which contains masses of sperm. The female duct is lined with a very low, anucleated epithelium and surrounded by a circular muscle sheath. In some individuals the
epithelium becomes a pseudocuticula close to the bursa. More or less in the middle
Porrocystidinae of the Galapagos
319
of its length there is a bundle of eosinophilic glands, arranged in a circle around the
duct. Just proximal to these glands, the circular muscles form a sphincter of four
fibers. After that, the female duct widens and contains a large amount of sperm,
clearly functioning as the seminal receptacle. The spermatic ducts and the oviducts
B
A
p
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VS
acg
vg
br
ma
vi
ph
c
)}
VS
vg
acg
s
ut
c
2011m
gp
ov
b
gp
Fig. 6. - Pygmorhynchus pygmaeus n. gen. n. sp. A, general structure; B, male atrial organs; C, stylet; D, reconstruction of the atrial system from the right side; (A-C from live animals).
320
T.J. Artois and E.R. Schockaert
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open here. In the holotype, the openings of the spermatic ducts and of the oviducts
are clearly separated, with the oviducts opening most distally. In other specimens
these openings lie much nearer to each other, connected to the seminal receptacle at
Fig. 7.- Pygmorhynchus pygmaeus n. gen. n. sp. A, live animal (part behind the proboscis); B, atrial organs; C, prostate vesicle with stylet; (all from live animals)
Porrocystidinae of the Galapagos
321
almost the same place. The spermatic ducts are very short and surrounded by thick
circular muscles, leaving the seminal receptacle from both sides. The oviducts, lined
with a low, nucleated epithelium and surrounded by longitudinal muscles, enter the
female duct through a common muscular pore. The vitelloducts enter the oviducts
near the ovaries. The uterus is of the normal polycystidid type.
Discussion. See the general discussion.
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GENERAL DISCUSSION
(Fig. 8)
EvooNIN (1977) erected the subfamily Porrocystidinae to contain the genera
Porrocystis Reisinger 1926, Austrorhynchus Kading 1952, Antiboreorhynchus Karling 1952, Phonorhynchus Graff 1905, Cincturorhynchus Evdonin 1970 and Megaloascos Evdonin 1970. Megaloascos psammophylum Evdonin 1970 is, in our opinion, insufficiently known and will not be discussed. These genera are characterized
(diagnosis of EVDONIN 1977, excluding Megaloascos) by paired gonads, accessory
hard parts present or not. accessory glandular reservoir present or not, male bursa
present or not, female bursa present or not. The new genera Pygmorhynchus and
Galapagorhynchus thus fit this diagnosis, and the genus Paraustrorhynchus Kading
& Schockaert 1977 can also be added to the group (considered related to Antiboreorhynchus and Austrorhynchus by KARLING & SCHOCKAERT 1977, but see discussion
below). We now consider a number of characteristics of these genera.
Except in Antiboreorhynchus and Paraustrorhynchus, the female system shows
a number of particular similarities: there is a terminal female bursa, and the ovaries are connected to the female duct not only by the oviducts, but also by so-called
insemination ducts (or spermatic ducts). The terminal female bursa is probably a
plesiomorphy (present in many polycystidids and also in other taxa, e.g. the Koinocystididae). The presence of insemination ducts may be a synapomorphy, present
only in these genera. Alcha Marcus 1949 also has paired insemination ducts (KARLING & ScHOCKAERT 1977), but these are of a different nature and probably not
homologous.
As in the vast majority of the Polycystididae, there is a prostate vesicle with a
double-walled stylet, undoubtedly homologous and clearly a symplesiomorphy for
the genera mentioned. This is indeed also the case for Paraustrorhynchus and Antiboreorhynchus, in contrast with the ideas of KARLING & SCHOCKAERT (1977) who
considered the double-walled stylet in these two genera as accessory.
In Galapagorhynchus, Pygmorhynchus, Cincturorhynchus, Phonorhynchus, Paraustrorhynchus and Antiboreorhynchus there are accessory glands in the male
system, which have their own muscle coats in the first four genera. A bundle of
accessory glands can be found in several Polycystididae, often also forming a reservoir with a muscular wall as e.g. in Typhlopolycystis Kading 1956, Limipolycystis
Schilke 1970, Psammopolycystis Meixner 1938, but of a completely different structure to that in Galapagorhynchus, etc. The accessory glandular reservoir of Phonorhynchus is again somewhat different. A bundle of accessory glands in the male
system, with or without a muscle sheath, clearly may have arisen several times and
thus may not necessarily be homologous. Accessory glands are absent in Porrocystis
and in Austrorhynchus.
T.J. Artois and E.R. Schockaert
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322
Accessory hard parts are present in all Porrocystidinae, except for Pygmorhynchus and Galapagorhynchus. If an accessory glandular organ is present, it is always
associated with the accessory hard part. This accessory hard part is a single-walled
tube in Phonorhynchus, but not in the other genera. The fact that the accessory
hard part is single-walled and tubiform is almost unique within the Polycystididae.
It is only encountered in the unrelated genera Phonorhynchoides Beklemishev 1927
and Annalis ella Karling 1978 and is a clear autapomorphy for Phonorhynchus.
In most of the Polycystididae with a copulatory organ of the divisa-type (terminology of KARLING 1956) the ejaculatory duct enters the male atrium near the
prostate vesicle and the double-walled stylet. In Cincturorhynchus, Galapagorhynchus and Pygmorhynchus, as well as in Paraustrorhynchus and Antiboreorhynchus
the ejaculatory duct enters the male atrium near the accessory glands and thus
near any accessory hard parts that are present. In Porrocystis (lacking accessory
glands) the ejaculatory duct also enters the male atrium near the accessory hard
part. Only in Austrorhynchus and Phonorhynchus is the ejaculatory duct associated
with the prostate stylet; the plesiomorphic situation.
In Phonorhynchus, Pygmorhynchus and Cincturorhynchus, nuclei are present
at the junction of the sheath epithelium with the cone epithelium. The same feature is also encountered in some genera of the Gyratricinae Graff 1905 (see KAR-
A
D
B
c
F
Fig. 8. - Schematic representation of the atrial organs of the six genera of Porrocystidinae as now
defined. A, Phonorhynchus; B, Austrorhynchus; C, Porrocystis; D, Cincturorhynchus; E, Pygmorhynchus; F, Galapagorhynchus.
323
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Porrocystidinae of the Galapagos
LING 1955). In all cases, electron microscopy revealed that these nuclei belong to
the apical cone epithelium and the proximal belt of the sheath epithelium (A. DE
VocHT unpublished data; see also ScHOCKAERT & BEDINI 1977 for Polycystis naegelii).
Conclusions concerning the phylogeny of these genera would be very tentative
at the moment and should include other taxa as well. However, the paired insemination ducts are unique and may represent a synapomorphic feature for the genera
in which they occur. This group can thus be considered monophyletic, under the
name Porrocystidinae. It contains all the genera that EvDONIN (1977) placed within
it (excluding Antiboreorhvnchus and Megaloascos: see above) and the two new genera presented in this contribution. Within the Porrocystidinae a possible monophyletic group is formed by the genera Porrocystis, Cincturorhynchus, Pygmorhynchus
and Galapagorhynchus sharing the feature of the ejaculatory duct shifted away
from the prostate vesicle. A synapomorphic feature for Galapagorhynchus and Pygmorhynchus may be the loss of the accessory stylet.
DIAGNOSES
Porrocystidinae Evdonin 1977 (emend. after EvnoNrN 1977). Polycystididae
with a proboscis with four retractors and a ventral pair of integument retractors.
Nuclei can be present in the junction between the proboscis cone and the proboscis
sheath epithelia. Gonads paired. With a double-walled stylet associated with a prostate vesicle. Accessory hard structure present or not. Accessory glandular organ
present or not. If both are present they are always associated with each other. Ejaculatory duct opens in the male atrium near the prostate organ or near the accessory organ (divisa type). The male atrium is always very broad and proximally more
or less divided into two compartments. Female duct mostly with a relatively strong
muscle coat, sometimes forming a strong sphincter. Paired spermatic ducts present.
Terminal female bursa present. Type genus: Porrocystis Reisinger 1926. Other genera: Austrorhynchus Kading 1952, Phonorhynchus Graff 1905, Cincturorhynchus
Evdonin 1970, Pygmorhynchus n. gen. and Galapagorhynchus n. gen.
Austrorhynchus galapagoensis n. sp. Austrorhynchus species with a stylet of 21
Jim long without hook, with tube and funnel of equal length. Accessory stylet 36
Jim, annular (or possibly a plate). With distal comb with fine teeth and a 41 Jim
long flagellum without comb.
Galapagorhynchus n. gen. Porrocystidinae without nuclei in the junction of
the proboscis cone and proboscis sheath epithelia. Common atrium very long. Two
glandular organs in the male system. One of them connected to a double-walled
stylet and thus considered a prostate. No accessory hard structures. Ejaculatory
duct opening in the male atrium near the accessory glandular organ. Male atrium
with small teeth in its proximal half. Spermatic ducts very long, the distal part narrow with a circular muscle coat. Female duct with a huge sphincter. Type species:
G. hoxholdi n. sp., provisionally with the same diagnosis as the genus. Stylet
double-walled, hook-shaped, ± 101 Jim long.
Pygmorhynchus n. gen. Porrocystidinae with nuclei in the junction of the proboscis cone and proboscis sheath epithelia. Two glandular organs in the male
system. One of them, the prostate vesicle, provided with a small, double-walled stylet. No accessory hard structures. Ejaculatory duct opening in the male atrium near
the accessory glandular organ. Spermatic ducts short and very muscular. Female
324
T.J. Artois and E.R. Schockaert
duct with glands arranged in a ring. Type species P. pygmaeus n. sp., provisionally
with the same diagnosis as the genus. Stylet very small (13.5 pm), double-walled
(?), slightly curved.
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ACKNOWLEDGEMENTS
Prof. Dr Peter Ax is acknowledged for sending us the sectioned material and the drawings and photographic material made by Dr Siegmar Hoxhold. The Galapagos Project was
financially supported by the Stiftung Volkswagenwerk. Dr Nikki Watson is thanked for the
critical reading of the manuscript. Mr Frank Van Belleghem is thanked for helping us with
the figures. This paper is a contribution to project G.0086.96, financed by the Fund of Scientific Research-Flanders (Belgium).
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